/*-------------------------------------------------------------------------
 *
 * dfmgr.c--
 *    Dynamic function manager code.
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    $Header: /usr/local/cvsroot/postgres95/src/backend/utils/fmgr/dfmgr.c,v 1.4 1996/11/27 08:16:07 bryanh Exp $
 *
 *-------------------------------------------------------------------------
 */
#include <sys/types.h>
#include <sys/stat.h>
#include <stdio.h>
#include <string.h>

#include "postgres.h"

#include "config.h"    /* for MAXPATHLEN */
#include "fmgr.h"		/* generated by Gen_fmgrtab.sh */
#include "utils/dynamic_loader.h"
#include "utils/elog.h"
#include "utils/builtins.h"
#include "access/heapam.h"
#include "nodes/pg_list.h"

#include "port-protos.h"     	/* system specific function prototypes */

#include "catalog/catname.h"
#include "utils/syscache.h"
#include "catalog/pg_proc.h"

static DynamicFileList *file_list = (DynamicFileList *) NULL;
static DynamicFileList *file_tail = (DynamicFileList *) NULL;

#define NOT_EQUAL(A, B) (((A).st_ino != (B).inode) \
                      || ((A).st_dev != (B).device))

static Oid procedureId_save = -1;
static int pronargs_save;
static func_ptr user_fn_save = (func_ptr) NULL;
static func_ptr handle_load(char *filename, char *funcname);

func_ptr
fmgr_dynamic(Oid procedureId, int *pronargs)
{
    HeapTuple   procedureTuple;
    Form_pg_proc procedureStruct;
    char        *proname;
    char        *probinattr, *probinstring;
    func_ptr    user_fn, handle_load();
    Relation    rdesc;
    bool     isnull;
    
    if (procedureId == procedureId_save) {
        *pronargs = pronargs_save;
        return(user_fn_save);
    }
    
    /*
     * The procedure isn't a builtin, so we'll have to do a catalog
     * lookup to find its pg_proc entry.
     */
    procedureTuple = SearchSysCacheTuple(PROOID, ObjectIdGetDatum(procedureId),
					 0,0,0);
    if (!HeapTupleIsValid(procedureTuple)) {
        elog(WARN, "fmgr: Cache lookup failed for procedure %d\n",
             procedureId);
        return((func_ptr) NULL);
    }
    
    procedureStruct = (Form_pg_proc) GETSTRUCT(procedureTuple);
    proname = procedureStruct->proname.data;
    pronargs_save = *pronargs = procedureStruct->pronargs;
    
    /*
     * Extract the procedure info from the pg_proc tuple.
     * Since probin is varlena, do a amgetattr() on the procedure
     * tuple.  To do that, we need the rdesc for the procedure
     * relation, so...
     */
    
    /* open pg_procedure */
    
    rdesc = heap_openr(ProcedureRelationName);
    if (!RelationIsValid(rdesc)) {
        elog(WARN, "fmgr: Could not open relation %s",
             ProcedureRelationName);
        return((func_ptr) NULL);
    }
    probinattr = heap_getattr(procedureTuple, (Buffer) 0,
			      Anum_pg_proc_probin,
			      RelationGetTupleDescriptor(rdesc), &isnull);
    if (!PointerIsValid(probinattr) /*|| isnull*/) {
        heap_close(rdesc);
        elog(WARN, "fmgr: Could not extract probin for %d from %s",
             procedureId, ProcedureRelationName);
        return((func_ptr) NULL);
    }
    probinstring = textout((struct varlena *) probinattr);
    
    user_fn = handle_load(probinstring, proname);
    
    procedureId_save = procedureId;
    user_fn_save = user_fn;
    
    return(user_fn);
}

static func_ptr
handle_load(char *filename, char *funcname)
{
    DynamicFileList     *file_scanner = (DynamicFileList *) NULL;
    func_ptr            retval = (func_ptr) NULL;
    char                *load_error;
#ifdef WIN32
    struct _stat        stat_buf;
#else
    struct stat	stat_buf;
#endif     /* WIN32 */

    /*
     * Do this because loading files may screw up the dynamic function
     * manager otherwise.
     */
    procedureId_save = -1;

    /*
     * Scan the list of loaded FILES to see if the function
     * has been loaded.  
     */
    
    if (filename != (char *) NULL) {
        for (file_scanner = file_list;
             file_scanner != (DynamicFileList *) NULL
             && file_scanner->filename != (char *) NULL
             && strcmp(filename, file_scanner->filename) != 0;
             file_scanner = file_scanner->next)
	    ;
        if (file_scanner == (DynamicFileList *) NULL) {
            if (stat(filename, &stat_buf) == -1) {
                elog(WARN, "stat failed on file %s", filename);
            }
	    
            for (file_scanner = file_list;
                 file_scanner != (DynamicFileList *) NULL
                 && (NOT_EQUAL(stat_buf, *file_scanner));
                 file_scanner = file_scanner->next)
		;
            /*
             * Same files - different paths (ie, symlink or link)
             */
            if (file_scanner != (DynamicFileList *) NULL)
		(void) strcpy(file_scanner->filename, filename);
	    
        }
    } else {
        file_scanner = (DynamicFileList *) NULL;
    }
    
    /*
     * File not loaded yet.
     */
    
    if (file_scanner == (DynamicFileList *) NULL) {
        if (file_list == (DynamicFileList *) NULL) {
            file_list = (DynamicFileList *)
		malloc(sizeof(DynamicFileList));
            file_scanner = file_list;
        } else {
            file_tail->next = (DynamicFileList *)
		malloc(sizeof(DynamicFileList));
            file_scanner = file_tail->next;
        }
	memset((char *) file_scanner, 0, sizeof(DynamicFileList));
	
        (void) strcpy(file_scanner->filename, filename);
#ifndef WIN32
        file_scanner->device = stat_buf.st_dev;
        file_scanner->inode = stat_buf.st_ino;
#endif /* WIN32 */
        file_scanner->next = (DynamicFileList *) NULL;
	
	file_scanner->handle = pg_dlopen(filename);
        if (file_scanner->handle == (void *)NULL) {
	    load_error = (char *) pg_dlerror();
            if (file_scanner == file_list) {
                file_list = (DynamicFileList *) NULL;
            } else {
                file_tail->next = (DynamicFileList *) NULL;
            }
	    
            free((char *) file_scanner);
            elog(WARN, "Load of file %s failed: %s", filename, load_error);
        }
	
	/*
	 * Just load the file - we are done with that so return.
	 */
        file_tail = file_scanner;
	
        if (funcname == (char *) NULL)
	    return((func_ptr) NULL);
    }
    
    retval = (func_ptr) pg_dlsym(file_scanner->handle, funcname);
    
    if (retval == (func_ptr) NULL) {
	elog(WARN, "Can't find function %s in file %s", funcname, filename);
    }
    
    return(retval);
}

/*
 * This function loads files by the following:
 *
 * If the file is already loaded:
 * o  Zero out that file's loaded space (so it doesn't screw up linking)
 * o  Free all space associated with that file 
 * o  Free that file's descriptor.
 *
 * Now load the file by calling handle_load with a NULL argument as the
 * function.
 */
void
load_file(char *filename)
{
    DynamicFileList *file_scanner, *p;
#ifdef WIN32
    struct _stat stat_buf;
#else
     struct stat stat_buf;
#endif /* WIN32 */

    int done = 0;
    
    if (stat(filename, &stat_buf) == -1) {
        elog(WARN, "stat failed on file %s", filename);
    }
    
    if (file_list != (DynamicFileList *) NULL
	&& !NOT_EQUAL(stat_buf, *file_list)) {
        file_scanner = file_list;
        file_list = file_list->next;
	pg_dlclose(file_scanner->handle);
        free((char *) file_scanner);
    } else if (file_list != (DynamicFileList *) NULL) {
        file_scanner = file_list;
        while (!done) {
            if (file_scanner->next == (DynamicFileList *) NULL) {
                done = 1;
            } else if (!NOT_EQUAL(stat_buf, *(file_scanner->next))) {
                done = 1;
            } else {
                file_scanner = file_scanner->next;
            }
        }
	
        if (file_scanner->next != (DynamicFileList *) NULL) {
            p = file_scanner->next;
            file_scanner->next = file_scanner->next->next;
	    pg_dlclose(file_scanner->handle);
            free((char *)p);
        }
    }
    handle_load(filename, (char *) NULL);
}
